Figure 1

(a) Top view of the noncollinear interaction area where two UV filaments interfered to create a plasma grating, with a FW probe beam passing through the interaction region at the Bragg incident angle. 1st: the first-order Bragg diffraction; MS: microscope with CCD; EM: pulse energy meter. (b) Plasma fluorescence distribution from plasma channels induced by the interacting TH femtosecond pulses.Reuse & Permissions

Figure 2

(a) Photograph of light spots projected on a white paper screen placed 0.5 m after the filament intersecting point recorded by a digital camera. (b) 3D spatial intensity distribution of the FW beams after passing through the plasma grating. (c) Distribution of laser intensity along $y$ axis after single-slit diffraction from the intersecting filaments.Reuse & Permissions

Figure 3

Bragg diffraction efficiency induced by plasma grating (black circles) and peak electron density (blue or gray squares) inside the plasma grating versus the incident FW pulse energy.Reuse & Permissions

Figure 4

Measured peak electron density inside the plasma grating as a function of time delay between the FW and plasma grating forming TH laser pulses.Reuse & Permissions

Figure 5

Experimentally observed fluorescence spectra from the plasma grating induced by two interfering TH pulses (blue or bottom curve), from plasma grating with a Bragg incident FW pulses of 10 mJ delayed 3.6 ps with respect to the TH pulses (black or middle curve), and from plasma grating with two Bragg incident FW pulses of 5 mJ subsequently delayed 3.6 and 7.2 ps with respect to the TH pulses (red or upper curve), respectively. The emission wavelengths were marked above the corresponding peaks for atomic ions and highly ionized ions. A dramatic increase of plasma and ionic fluorescence indicated impact ionization in the preformed plasma channels.Reuse & Permissions